I love Categories and use it to organize my apps on my iPhone but it takes forever to load a folder, especially when it contains a lot of apps. Two recent application upgrades have really helped with this problem. 

Backgrounder allows you to run processes in the background and the new version of Categories(2.2) takes advantage of this new functionality. By using the Background feature, you can set up folder by folder background loading. This makes it lightning fast to open  folders. In normal iPhone mode, open the folder you want to speed up. Press and hold the menu button until you see the message, “Backgrounding Enabled”. It will exit the folder but opening it again will be really fast. Press and hold the menu button again while the folder is opened to turn it off.